SemObsCov ctor: restrict n_obs to integer

don't allow missing n_obs

Author: alyst

src/observed/covariance.jl

@@ -47,13 +47,13 @@ struct SemObservedCovariance{B, C} <: SemObserved
 end
 
 function SemObservedCovariance(;
-    specification::Union{SemSpecification, Nothing},
+    specification::Union{SemSpecification, Nothing} = nothing,
     obs_cov,
     obs_colnames = nothing,
     spec_colnames = nothing,
     obs_mean = nothing,
     meanstructure = false,
-    n_obs = nothing,
+    n_obs::Integer,
     kwargs...,
 )
     if !meanstructure & !isnothing(obs_mean)

test/unit_tests/data_input_formats.jl

@@ -209,7 +209,7 @@ end
     )
 end
 
-@test_throws UndefKeywordError(:specification) SemObservedCovariance(obs_cov = dat_cov)
+@test_throws UndefKeywordError(:n_obs) SemObservedCovariance(obs_cov = dat_cov)
 
 @test_throws ArgumentError("no `obs_colnames` were specified") begin
     SemObservedCovariance(specification = spec, obs_cov = dat_cov, n_obs = 75)